Opaquing agent for vitreous enamels



Patented Dec. .22, 1942 UNITED STATES PATENT OFFICE OPAQUING AGENT FORVITREOUS Carl J. Harbert, Shaker Heights, and Clarence A. Beabright,Cleveland, Ohio, assignors to The Harshaw Chemical Company, Elyria,Ohio, a

corporation of Ohio No Drawing. Application September 26, 1940, SerialNo. 358,558

11 Claims. (Cl. 106-312) This invention relates to opaqulng agents forvitreous enamels and particularly to novel compositions of superioropaquing properties.

In U. S. Patent No. 2,199,794 to Harshaw and Stillwell there isdescribeda class of opaquing agents containing oxides of calcium, antimony andtitanium together with calcium fluoride or other fluoride and containingthese elements or constituents in preferred proportion approximatelycorresponding to the empirical formula.

and with from to 30% of 'CaFz or other fluoride. These compositions areexcellent opaquing agents and have been widely used.

We have now discovered that we are able to produce compositions ofsomewhat different proportions but similar to those of the Harshaw andStillwell patent and which are capable of imparting to vitreous enamelsunder conditions of commercial use a substantially greater opacityaccompanied by a very much improved fusibility. Opaquing value isdetermined by the total refiectance of the resulting enamel and theshape of the color curve, magnesium oxide being taken as a standard andthe reflectance being expressed in terms of per cent of the reflectanceof the standard. Measured in this way we find that our novelcompositions, at optimum proportions, are definitely superior to tinoxide as opaquing agents. Fusibility may be measured likewise bycomparison with a standard, suitably tin oxide. Equal amounts of thestandard and the opacifl'er to be tested are made into a slip using thesame amounts of the same frit and other ingredients necessary. The slipis dried, and the flowability of the two dried slips is tested at atemperature which will cause at least one of them to flow appreciably.Tested in this way, we find that our novel compositions, at optimumproportions, exhibit fusibility approximately that of tin oxide anddefinitely superior to that of the compositions of the Harshaw andStillwell patent referred We consider the optimum composition to be: Percent CaO 24.6

813205 40.5 T102 30.0 CaFa 4.9

This corresponds to an empirical formula:

3 /gCtO Ca.F'2 'Sb2053T102 Considerable latitude is possible withoutloss of the superior character of the product but the 'We do not wish tobe understood as representing that we have produced compositions notcontaining any fluoride which are equal to the best compositionsproduced according to the Harshaw and Stillwell patent in respect toreflectance. We have not. Such compositions do, however, exhibitsuperior fusibility and are capable at the optimum proportion ofproducing reflectance approaching closely to that produced by tin oxide.

The above indicated limits approximate the following suitable proportionlimits:

Molecular weights SbzOs --a 1 T102 1to4 CaO 3to4 /2 CaFz to 1 Asindicated, it is possible to omit CaFz altogether and still obtain avaluable product.

i We prefer to produce compositions of even closer proportion limits, asfollows:.

Molecular weights SbzOs 1 TiOz 1.3 to 3.0 08.0 3.5 to 4.0 CaFz 0.4 to0.6

In the event no fluoride is used, we prefer to produce compositionswithin the following proportion limits:

Molecular Weights SbzOs 1 T102 1 to4 A; 0&0 3% to 4 These compositionsmay be produced by calcining under oxidizing conditions, Sb2O3,-'-IiO2,Cam and a suitable source of CaO, such as'CaO, Ca(OH)2, CaCOa, Ca(NO3)zor mixtures thereof.

Calcination preferably is carried out at a temperature from 1000 C. to1200 C., batch temperature, in an oxidizing atmosphere. The timerequired varies according to the temperature and other conditions,particularly the size of the batch, larger batches requiring longertime. The

reflectance is nearly fully developed by 1% hours firing at 1150' 0.,whereas three or more hours are desirable at 1000 C. While otherconditions may be used successfully, we prefer to fire for three hoursor longer at from 1000 C. to 1150 C.

or two hours or longer at 1100 C. to 120Q C.

In the preferred practice of the invention we make use of batchcompositions within the following proportion limits:

Molecular weights SbzOa 1 T102- 1 to 4 /2 CaCO: 50% to 90% Ca(OH): 50%to 10%} Between-m 3 CaF- V4 to 1 Most desirably we operate within thefollowing limits:

Molecular weights TiOr is to 3.0 CaCO: 70% to 80% Ca(OH): 30% to 20%} 3%4 cm 0.4 to 0.6

The following examples will serve to illustrate the invention:

Example I A batch was prepared by admixing thoroughly in dry powder formthe following:

Parts by weight SbrOa 83 T: 480 CaCO: 600 CaiOHh '74 Cal '18 This batchwas calcined at 1150 C. for 2 hours in an oxidizing atmosphere.

Example If The foregoing example may be varied by employing any of thefollowing batch compositions:

The above described compositions are suitable for mill additions and arepreferably used at 2% to 10% and usually at about 4% to 6%.

We do not know the final state of combination of the oxides in thecalcination products and accordingly refer to such products ascontaining the constituent oxides and fluoride.

Having thus described our invention, what we claim is:

1. A new composition of matter suitable for use as an opaquing agent,the same being the product of calcining under oxidizing conditionsmaterials capable of yielding:

Molecular weights BbzOs 1 T102 1 to 4V: CaO, between. 3 and 4% 2. A newcomposition of matter suitable for use as an opaquing agent, the samebeing the product of calcining under oxidizing conditions materialscapable of yielding:

Molecular weights SbaOs 1 T10: 1.3 to 3.0 CaO, between 3 and 4% Cal": /4to 1 3. A new composition of matter suitable for use as an opaquingagent, the same being the product of calcining under oxidizingconditions materials capable of yielding:

. Molecular weights SbeOs 1 TiO: 1.3 to 3.0 CaO 3.5 to 4 Cal": 0.4 to0.6

4. A new composition of matter suitable for use as an opaquing agent,the same being the product of calcining under oxidizing conditionsmaterials capable of yielding:

Molecular weights SbaOt 1 1 to 4% CaO 3% to 4% 5. A new composition ofmatter suitable for use as an opaquing agent, the same being the productof calcining under oxidizing conditions materials capable of yieldingapproximately:

Molecular weights SD20: 1 T102 3 Ca() 3% Cal: 36

6. A new composition of matter suitable for use as an opaquing agent,the same being the product of calcining under oxidizing conditionsmaterials capable of yielding approximately:

Molecular weights Sb:Os 1 T10: 3 CaO 4 'l. A process of making anopaauing agent for vitreous enamels comprising calcining under oxidizingconditions and at temperatures from 1000' C. to 1200 0., SbaOa, T102.Cam, and a source of CaO from the group consisting of CaO, Ca(OH) CaCOa,Ca(NOs): and mixtures thereof, the proportions being such as to producea composition fonflaining in the indicated proportions the 101-Molecular weights Sha 1 T10- 1 to 4% CaO, between 3 and 4% 8. A processof preparing an opaquing agent for vitreous enamels comprising calciningin an oxidizing atmosphere a batch or the following composition andproportions:

Molecular weights Sha 1 T 1 to 4 CaCOa 50% to 90%} To yield CaO, Ca(OH)a50% to 10% more than 3 an (1 less than.. 4 Cal: A to 1 9. A process ofpreparing an opaqulng agent for vitreous enamels comprising calcining inan oxidizing atmosphere a bath of the following composition andproportions:

Molecular weights T m 1.3 to 3.0 CaCOa 70% to 80% Ca(OH)z30% to20%l'yield 4 can 0.4 to 0.6

10. A new composition oi! matter comprising the product oi calciningunder oxidizing conditions the following:

11. A new composition of matter comprising the product or calciningunder oxidizing conditions the following:

Molecular weights Sbz 1 TiO- q 0 1 3 to 3 0 CaCO: 70 a to 8 o Ca(0H)z to20%} yield 3% 4 Car: 04 to 0 6 CARL J. HARBERT. CLARENCE A. SEABRIGHT.

CERTIFICATE OF conhnqzxdn. Patent no. 2, 306,557. December 22, 19!;2.

' cARL' J; HARBERT, ,ET AL.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 2,.first column, iine 61, for Molecular weight read --Partsbyweight--;and that the said Letters- Batent should be read with this correctiontherein that the same may conform -to the record of the case in'thePatent Office Signed and sealed this 9th day of February,-A. D. 1%}.

Henry Van Arsdale, (Seal) Acting Commissioner of Patents.

